I don't understand your question... Or you don't understand root.
Almost every custom ROM is pre-rooted, there is no issue here. Just do a nandroid backup in recovery, wipe, and flash ROM and you will be good to go.
Sent from my Nexus 4 using Tapatalk
Current Personal Phone: Google Nexus 4 on Cricket/Aio (Beanstalk
4.4.4 with hells-Core Kernel
Current Work Phone: LG G2 VS980 on VZW (Official Beanstalk
Current Tablet: iPad 4 and Samsung Galaxy Note Pro 12.2
Other phones "in the family": HTC DNA, HTC One (M7), Motorola Moto G GPE
Previous/Retired Android Devices: HTC Aria, HTC Incredible 2, HTC Rezound, Samsung Stratosphere, Samsung Galaxy S2 Skyrocket, Nextbook 8P